Power Circuits & Overloads

These days we’ve come to depend on electricity for our day to day lives. For food (both preparation and cooking), communication, work and even now commuting. As result it be frustrating or in some cases even hazardous when we loose supply. While electricity arrives at our homes via a single cable, either overhead or underground, after the power makes it way through your smart meter and into the switchboard it then splits into individual circuits for various specialist or general purposes.

Types of electrical circuits

Power circuits, and their associated protection devices (switches), found in your switchboard can be for a variety of purposes. You’ll commonly find circuit and circuit breakers for Ovens, Hot Plates, Air Conditioners, Hot Water Units, Solar, Lighting, General Power Outlets and Sub Mains that feed other switchboards (sub-boards). The cabling that makes us these circuits will be chosen based on the maximum demand required or likely to be required from a given appliance. This wiring can also vary in maximum operating temperature, and number of conductors. Three Phase wiring needs an extra two conductor than Single Phase wiring and appliances such as Hot Water Systems often need an extra wire for the purpose of delivery off peak power at cheaper rates.

Type of circuit protection

With the huge variance in the performance and specs of different wiring it is critical the pairing of protection device (circuit breaker) and cable is correct. When the wrong circuit breaker or safety switch is used with any given cable the breaker ends up providing no protection at all. So for a circuit breaker no overload/fire protection is present and for a RCD(s) (Safety Switch[es]) no protection from electrocution is present. Thus when a circuit is overloading it is never ok to simply upsize the circuit breaker, rather the cabling and breaker must be replaced and upsized.

Why a circuit might trip and how to fix it

A power circuit will commonly trip for one of three reasons; short-circuit, overload or earth-leakage. Short-circuit will usually be caused by someone or something damaging the cabling. Overload will most often be caused by the simultaneous use of power hungry appliances that share a circuit. Earth-leakage is measured by an RCD (Safety Switch) and occurs when you, a family member or water come into contact with the electricity. As such you’ll want to ensure you have one or more RCD (Safety Switch), a surprising number of homes do not. When a power circuit is overloading, the circuit breaker had measured that the load being drawn by the appliances on the circuit is too much for the cabling. This will also occur when a wire is damaged and creates a short-circuit. While a short-circuit can often be repaired and overload requires that the load on the cable is lowered, or the cabling and circuit breaker is upsized. When an overload occurs on a general power circuit it is rarely economically viable to upsize all the cabling. Rather, an electrician will add an additional circuit to the switchboard and split the load across the two circuits to halve the load on the original cable.